Without limiting the scope of the invention, its background is described in connection with electric field sensors.
U.S. Pat. No. 6,922,059 issued to Zank et al. (2005) discloses a detection system comprising inexpensive, miniaturized sensors for detecting electric field (E-field) disturbances. Such sensors are easily and covertly deployable and have low power consumption. The devices may incorporate visual or audio alerts and can include communications hardware for transmitting data for further processing of the electrostatic events.
United States Patent Application No. 20080238433 (Joutsenoja and Kyyny, 2008) describes a sensor product for electric field sensing. The sensor includes a substrate, at least one electrically conductive area on the surface of the substrate, an output, and at least one conductor between the at least one electrically conductive area and the output.
United States Patent Application No 20090091329 (Barsukov et al., 2009) discloses a sensor for marine measurements of an electric field, the sensor includes at least two electrodes; signal transmission means for transmitting measured signals from the sensor to a signal processing unit; at least two closed containers which are formed on a non-conductive material and are filled with an electrolyte; at least two flexible hoses formed of an electrically non-conductive material; there being attached in a fluid-communicating manner to each of the containers at least one first hose end, and a second hose end being open and attached to means for exact positioning of the second hose end; the hoses being arranged to be filled with a medium of the same type as that, in which the sensor is arranged to be immersed in an operative condition; and two containers forming a pair of containers, the two containers, relatively, being placed close to each other under approximately identical thermal, pressure and chemical conditions.